Android: If someone tries unsuccessfully to unlock your phone, you'd probably like to know who and where. Lockwatch serves your need by emailing you a GPS-tagged photo of an intruder when they fail.

The app is bare bones as it serves a very specific purpose. It's not a total security tool ("total security" being a misnomer on phones anyway), but if you have sneaky friends, paranoid family members, or just want to be able to give that little extra something to the police if you get robbed, Lockwatch can help. If you don't already have a more full security system in place, you can start with Google's own Android Device Manager.